1. Field of the Invention
The present invention relates to a display control system for a raster-scanning type display unit having the function of automatically adjusting the image display position on a screen on the basis of the difference in phase between a horizontal synchronizing signal and a display position signal.
2. Description of the Related Art
FIG. 1 shows a conventional display control system. In FIG. 1, a reference numeral 1 denotes a display control circuit for generating horizontal and vertical synchronizing signals and a video signal for display; 2, a video signal; 3, a vertical synchronizing signal; 4, a horizontal synchronizing signal; 5, a video control circuit; 6, a vertical deflection circuit; 7, a horizontal deflection circuit; 8, a cathode-ray tube; 9, a display control unit; and 10, a display unit.
FIG. 2 shows a horizontal synchronizing signal and a video signal which are output from the conventional display control system. In FIG. 2, reference numerals 4a and 2a respectively denote a horizontal synchronizing signal and a video signal which are output in the display mode `a`.
Reference numerals 4b and 2b respectively denote a horizontal synchronizing signal and a video signal which are output in the different display mode `b`.
In the above-described display control system, the display unit 10 is adjusted such that it displays the video signal 2a at the center of the screen by the relative timing between the horizontal synchronizing signal 4a and the video signal 2a. Therefore, when the horizontal synchronizing signal 4b and the video signal 2b which provide a different relative timing are supplied to the display unit 10, since the video signal 2b is displayed at the position on the screen which is adjusted on the basis of this relative timing, the video signal is displayed off the center position by the distance equal to the difference "t" between the relative timings of the signals 4a, 2a and 4b, 2b.
In the thus-arranged conventional display control system, in order to cope with the display modes having different timings, separate display units corresponding to the individual timings must be connected to the display control unit. Furthermore, signal interfaces which adopt different signal transmission methods must be provided on both the display control unit and the display unit and then a signal cable is provided between the units. These make the entire structure of the system complicated and expensive.